What is dementia?

Dementia afflicts a great number of elderly people but it is difficult to diagnose clinically. However, the National Institute of Neurological and Communicative Disorders and Stroke (NINCDS) and the Alzheimer’s Disease and Related Disorders Association (ADRDA) have provided diagnostic guidance, which were updated most recently in 2011. The NINCDS and ADRDA specify that general dementia is defined as: having a condition which interferes with the ability to function at work or during usual activities, which represents a decline from previous levels of function, which is not explained by delirium or major psychiatric disorder, and which can be defined as a cognitive impairment (involving either impaired memory, reasoning, language or visual-spatial abilities or changes in personality) (McKhann et al.).

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What is the current prevalence of dementia?

The current worldwide prevalence of dementia is remarkably high in elderly people and increases very rapidly with age. While the geography also appears to influence the incidence markedly, some researchers have suggested that this is more a function of the methodology used by the researchers working with those populations (e.g. Fratiglioni et al.). The following table sets out the findings of a number of studies:

Study

Geography

Population

Prevalence

Plassman et al.

United States

males and females aged >71 years

13.9%

Plassman et al.

United States

males aged >71 years

11.1%

Plassman et al.

United States

females aged >71 years

15.7%

Plassman et al.

United States

males and females aged 71 – 79 years

5.0%

Plassman et al.

United States

males and females aged 80 – 89 years

24.2%

Plassman et al.

United States

males and females aged >90 years

37.4%

Ferri et al.

The Americas

males and females aged 80 – 84

11.1 – 14.8%

Ferri et al.

The Americas

males and females aged >85

28.1 – 33.2%

Ferri et al.

Europe

males and females aged 80 – 84

11.8 – 12.2%

Ferri et al.

Europe

males and females aged >85

24.5 – 24.8%

Ferri et al.

North Africa and the Middle East

males and females aged 80 – 84

4.3 – 7.0%

Ferri et al.

North Africa and the Middle East

males and females aged >85

9.7 – 14.9%

Ferri et al.

Africa

males and females aged 80 – 84

13.6 – 13.9%

Ferri et al.

Africa

males and females aged >85

23.5 – 25.5%

Ferri et al.

South Asia

males and females aged 80 – 84

7.2 – 10.8%

Ferri et al.

South Asia

males and females aged >85

14.4 – 17.6%

Ferri et al.

Western Pacific

males and females aged 80 – 84

10.4 – 14.4%

Ferri et al.

Western Pacific

males and females aged >85

22.1 – 26.2%

Graham et al.

Canada

males and females aged >65 years

8.0%

Dong et al.

China

males and females aged >60 years

2.4%

Nitrini et al.

Latin America

males and females aged >60 years

7.0%

Lobo et al.

Europe

males and females aged 65 – 69 years

0.8%

Lobo et al.

Europe

males and females aged >90 years

28.5%

Fratiglioni et al.

Worldwide

males and females aged 60 to 64 years

0.3 – 1.0%

Fratiglioni et al.

Worldwide

males and females aged >95 years

42.3 – 68.3%

Based on these studies, it appears that the prevalence of dementia ranges widely depending on the exact age of the elderly population studied, with the prevalence in groups aged 60 – 64 years being as low as 0.3% and in groups aged >95 years being as high as 68.3%.

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What is the forecast prevalence of dementia?

The prevalence of dementia is thought to be increasing as a result of the ageing population. The following studies have produced estimates of the prevalence of dementia over varying timespans, as shown in the table below:

Study

Finding

Mura et al.

The researchers produced a model to calculate an estimate for the number of dementia cases expected to occur in France and Europe over the next few decades to 2050. They estimated that in France, in 2010, the number of dementia cases would be 754,000 (1.2% of the general population and 7.9% of the population >65 years) and that this would reach 1,813,000 cases (2.6% of the total population and 9.6% of the population >65 years) by 2050. Similarly, they estimated that in Europe dementia prevalence would be 6 million in 2010 (7.0% of the population >65 years) and 14 million in 2050 (10.1% of the population >65 years).

Wimo et al.

The researchers estimated the worldwide occurrence of dementia from 1950 – 2050 based on worldwide demographics of the elderly and age-specific prevalence and incidence values of dementia. They estimated that the number of people in the world with dementia in 2000 as 25 million (about 0.5% of the worldwide population) and that around 6.1% of the population >65 years had dementia. The researchers forecast that the prevalence of dementia would increase quickly from 25 million in 2000 to 63 million in 2030 and to 114 million in 2050.

Jorm et al.

The researchers produced an projection of the number of dementia cases in Australia from 2000 to 2050 using data from several meta-analyses of dementia prevalence and incidence in combination with age-specific population projections. They reported that prevalence of dementia was estimated to increase from 172,000 in 2000 to 588,000 in 2050 and that the incidence of dementia was estimated to increase from 43,000 to 143,000 new cases per year.

Based on these studies, it appears that the most recent estimate of the forecast worldwide prevalence of dementia in 2050 is around 114 million cases, while the forecast prevalence for Europe is 14 million cases.

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Is physical inactivity a risk factor for dementia?

While the main risk factor that is associated with dementia is older age, more and more research is recognizing that physical activity is also a significant factor, as shown in the following table:

Study

Method

Finding

Laurin et al.

The researchers followed a community sample of 9,008, randomly selected Canadian males and females aged >65 years. Of the 6,434 cognitively normal subjects at baseline, 4,615 completed a 5-year follow-up.

The researchers found that physical activity was associated with significantly lower risks of cognitive impairment, Alzheimer disease and all types of dementia of any type when compared with no activity. They also observed trends for a dose-response, with higher levels of physical activity being associated with further risk reductions.

Yaffe et al.

The researchers studied 5,925 predominantly white community-dwelling females aged >65 years without baseline cognitive impairment or physical limitations. Cognitive performance was measured using a modified Mini-Mental State Examination test at baseline. The researchers followed-up the subjects 6 – 8 years later and cognitive decline was defined as a >3-point decline on the same Mini-Mental State Examination test.

The researchers found that females with a greater physical activity level at baseline were less likely to experience cognitive decline during follow-up. Specifically, the researchers reported that in the highest and lowest quartiles of physical activity, cognitive decline occurred in 17% and 24% of subjects. The researchers noted that females in the highest quartile of physical activity were significantly less likely to develop cognitive decline than those in the lowest quartile, even after adjusting for age and educational level.

Podewils et al.

The researchers performed a prospective study to assess the association between physical activity and risk of dementia, Alzheimer's disease and vascular dementia in a population of 3,375 men and women aged >65 years in the United States who were free of dementia at baseline. The researchers reported 480 cases of dementia over an average of 5.4 years of follow-up.

The researchers reported that those subjects in the highest quartile of physical energy expenditure had a lower risk of dementia than those in the lowest quartile. The researchers also reported that those subjects who developed dementia were more likely to have at baseline: a lower educational level, the apolipoprotein (APOE) epsilon-4 allele, poorer cognitive performance, more physical difficulties, white-matter disease on cerebral MRI, a history of stroke, cardiovascular disease or hypertension.

Larson et al.

The researchers performed a prospective study to assess the association between physical activity and dementia in a population of 1,740 persons aged >65 years in the United States who were free of cognitive impairment at baseline. The researchers reported 158 cases of dementia over an average follow-up period of 6.2 years.

The researchers reported that the incidence rate of dementia was 13.0 per 1000 person-years for subjects who exercised >3 times per week compared with 19.7 per 1000 person-years for those who exercised <3 times per week. The researchers also found that having the apolipoprotein (APOE) epsilon-4 allele, poorer cognitive performance, more physical difficulties, diabetes, hypertension, cerebrovascular disease, coronary heart disease and depression were also associated with an increased risk of dementia but alcohol consumption, smoking, supplement use and educational level were not associated with an altered risk of dementia.

Andel et al.

The researchers performed a prospective twin study and a case-control study to assess the association between physical activity in mid-life and the risk of developing dementia in later life. The case-control analyses included 264 cases with dementia and 2,870 controls while the twin analyses included 90 twin pairs discordant for dementia.

In the case-control study, the researchers found that individuals who performed no exercise had a 1.6 and 2.9 times greater risk of developing dementia than those who performed light exercise such as gardening or walking or regular exercise involving sports, respectively. In the twin study, the researchers found a marked but non-significant association between higher levels of exercise and lower odds of dementia.

Abbott et al.

The researchers performed a prospective study to assess the association between walking and future risk of dementia in 2,257 physically capable older men. Over the follow-up period, the researchers identified 158 cases of dementia (15.6 per 1000 person-years).

The researchers reported that after controlling for age, the men who walked the least (<0.25 mile per day) had a 1.8 times greater risk of developing dementia than those who walked 2 miles per day. The researchers concluded that promoting active lifestyles in physically capable elderly men could improve cognitive function later in life.

Rovio et al.

The researchers performed a prospective study assess the association between leisure-time physical activity at mid-life and the subsequent development of dementia and Alzheimer's disease in 1,449 persons aged 65 – 79 who were followed-up over a 21-years period. The researchers found that 117 subjects developed dementia.

The researchers reported that performing leisure-time physical activity at mid-life >2 times per week was associated with a reduced risk of dementia and Alzheimer's disease even after controlling for age, sex, education, follow-up time, locomotor disorders, apolipoprotein (APOE) genotype, vascular disorders, smoking and alcohol intake.

Weuve et al.

The researchers assessed the correlation of long-term regular physical activity, including walking, with cognitive function in 18,766 females aged 70 – 81 years in the United States.

The researchers reported that higher levels of physical activity were associated with better cognitive performance. The researchers reported that in comparison with those in the lowest physical activity quintile, females in the highest quintile had a 20% lower risk of cognitive impairment. The researchers found similar results for walking as for general physical activity.

Verghese et al.

The researchers performed a prospective study to assess the association between leisure activities and the risk of dementia in a cohort of 469 community-dwelling subjects aged >75 years of age without dementia at baseline. The researchers found that over an average follow-up period of 5.1 years, 124 subjects developed dementia.

The researchers found that certain leisure activities were associated with a reduced risk of developing dementia, including reading, playing board games, playing musical instruments and dancing.

Schuit et al.

The researchers assessed the correlation between physical activity levels and the risk of cognitive decline during older age across carriers and non-carriers of the apolipoprotein (APOE) epsilon-4 allele in a cohort of 347 elderly Dutch men aged 74.6 ± 4.3 years at baseline. The researchers assessed the risk associated with either more or less than 1 hour of physical activity per day and cognitive decline was defined as a >3-point decline on a Mini-Mental State Examination test.

The researchers found that after adjusting for age, education, alcohol consumption, smoking and cognitive functioning at baseline, less physically active subjects were 2.0 times as likely to incur cognitive decline as active subjects. The researchers also found that carriers of the APOE epsilon-4 allele were also more likely to develop cognitive decline.

Barnes et al.

The researchers performed a prospective study to assess the association between baseline cardiovascular fitness and the risk of cognitive decline in a cohort of 349 non-institutionalized adults aged >55 years without cardiovascular disease, musculoskeletal disability or cognitive impairment at baseline, who were living in California. The researchers assessed cognitive decline using a Mini-Mental State Examination test.

The researchers reported that worse cardiorespiratory fitness at baseline was associated with greater cognitive decline over a 6-year period.

Lytle et al.

The researchers performed a prospective study to assess the association between exercise and cognitive decline in a sample of 1,146 individuals aged >65 years from a representative rural community. Cognitive decline was defined as a >3-point decline on the Mini-Mental State Examination test.

The researchers found that a high exercise level at baseline was associated a reduced risk of cognitive decline.

Based on these studies, it appears that individuals who habitually perform low levels of physical activity are at increased risk of developing dementia in later life.

Is poor body composition a risk factor for dementia?

While the main risk factor that is associated with dementia is older age, more and more research is recognizing that poor body composition is also a significant factor, as shown in the following table:

Study

Method

Finding

Whitmer et al.

The researchers wanted to assess the association between mid-life central obesity and the risk of developing dementia 3 decades later. Therefore, they performed a longitudinal analysis in 6,583 members of Kaiser Permanente of Northern California for whom a sagittal abdominal diameter was measured between 1964 – 1973 and who were assessed for dementia an average of 36 years later, between 1994 – 2006.

The researchers reported that 1,049 of the original 6,583 subjects (15.9%) were diagnosed with dementia. The researchers found that the subjects in the highest quintile of sagittal abdominal diameter had a 2.7 times greater risk of developing dementia than those in the lowest quintile.

Luchsinger et al.

The researchers performed a longitudinal study to assess the associations of body mass index (BMI) waist circumference and weight change to dementia, probable Alzheimer’s disease and dementia associated with stroke in a random sample of 893 Medicare recipients aged >65 years living in northern Manhattan, New York.

The researchers observed 181 cases of dementia cases over a mean follow-up period of 5.1 ± 2.6 years. The researchers reported that neither BMI nor waist circumference were linearly correlated with the risk of developing dementia.

Nourhashemi et al.

The researchers performed a prospective study to assess the association between body mass index (BMI) and the risk of dementia in a cohort of 3,646 non-institutionalized adults aged >65 years without cognitive disorders at baseline. The researchers followed up the subjects over an 8-year period.

The researchers reported that those subjects with a BMI of <21kg/m2 had a 1.48 times greater risk of developing dementia compared with subjects with a BMI of 23 – 26kg/m2. However, once individuals who developed dementia early during the follow-up period were excluded, this relationship was not significant. Since dementia is thought to lead to a reduction in bodyweight, this implies that a low BMI in itself is not a causal factor in leading to an increased risk of developing dementia.

Kivipelto et al.

The researchers wanted to assess the association between mid-life body mass index (BMI) and vascular risk factors, subsequent dementia and Alzheimer’s disease. Therefore, they recruited 1,449 subjects from the Cardiovascular Risk Factors, Aging, and Dementia (CAIDE) study and followed-up the subjects over an average period of 21 years.

The researchers found that obesity at midlife (BMI >30kg/m2) was associated with a 2.4 times greater risk of dementia and Alzheimer’s disease even after adjusting for socio-demographic variables. However, the association was reduced when adjusted for mid-life blood pressure, total cholesterol level, smoking, apolipoprotein (APOE) epsilon-4 genotype and history of vascular disorders. The researchers therefore concluded that mid-life obesity, high total cholesterol level and high systolic blood pressure are all significant risk factors for dementia.

Atti et al.

The researchers performed a prospective study to assess the association between late-life body mass index (BMI) and the risk of developing dementia in 1,255 subjects aged >75 years who were living in in Stockholm, Sweden.

The researchers found that those subjects who had a BMI of 20.0 – 24.9kg/m2 had a 1.33 times greater risk of developing dementia than subjects with a BMI of >25.0kg/m2.

Fitzpatrick et al.

The researchers performed a prospective cohort study to assess the associations between mid- and late-life obesity and the risk of developing dementia. The cohort comprised 2,798 adults without dementia at baseline with a mean age 74.7 years and the researchers followed-up the subjects after a mean 5.4 years.

The researchers found that individuals with a BMI classification of obese (BMI >30kg/m2) were 1.39 times more likely to develop dementia than individuals of normal weight (BMI 20 – 25kg/m2) even when adjusting for socio-demographic factors and cardiovascular risk factors. However, the researchers also found that individuals with a BMI classification of underweight (BMI <20kg/m2) also displayed a 1.62 times greater risk of developing dementia than normal weight individuals.

Whitmer et al.

The researchers performed a prospective cohort study to assess the associations between obesity in mid-life, measured by body mass index (BMI) and skinfold thickness, and risk of developing dementia. The cohort comprised 10,276 men and women who were members of Kaiser Permanente Northern California Medical Group.

The researchers reported that individuals with a BMI classification of obese (BMI >30kg/m2) had a 1.74 times greater risk of developing dementia than normal weight individuals (BMI of 18.6 – 24.9kg/m2), while overweight people (BMI of 25.0 – 29.9kg/m2) had a 1.35 times greater risk of developing dementia than normal weight individuals.

Rosengren et al.

The researchers performed a prospective population-based study to assess the associations between body mass index (BMI) and risk of developing dementia, as assessed by either hospital discharge or death certificate diagnosis of dementia. The researchers assessed a total of 7,402 males aged 47 – 55 years old in 1970 – 1973, without prior stroke or myocardial infarction. The researchers reported that 254 subjects (3.4%) had a hospital discharge diagnosis or a death certificate diagnosis of dementia during the follow-up period.

The researchers found that the relationship between BMI and dementia was not linear but rather men with a BMI between 20.00 – 22.49kg/m2 had the lowest risk. They found that in males with a BMI >22.5kg/m2, the risk of developing dementia increased linearly and obese males (BMI >30kg/m2) had a 2.54 times greater risk of developing dementia than those with an optimal BMI.

Gustafson et al.

The researchers performed a prospective study over a 32-year period of 1,462 females living in Sweden to assess the association between body mass index (BMI) and waist-to-hip ratio and the risk of developing dementia. Over the follow-up period, the researchers found that dementia occurred in 161 subjects.

The researchers reported that the relationship between BMI and the risk of developing dementia was not significant. However, they found that individuals with a mid-life waist-to-hip ratio of >0.80 in mid-life had a 2.2 times greater risk of developing dementia later in life.

Kanaya et al.

The researchers performed a prospective cohort study in 3,054 elderly people enrolled in the Health, Aging and Body Composition Study to assess the associations between adiposity measures (e.g. body mass index (BMI), waist circumference, sagittal abdominal diameter, total fat mass and subcutaneous and visceral fat) and cognitive decline, as measured by the change in the modified Mini-Mental State Examination score.

The researchers reported that males (but not females) in higher tertiles of total fat mass, sagittal abdominal diameter and subcutaneous fat displayed a significantly greater change in modified Mini-Mental State Examination scores than males in lower tertiles.

Wolf et al.

The researchers performed a prospective population-based study in a sample of 1,814 males and females aged 40 – 69 years taken from the community-based Framingham Offspring Study over a follow-up period of 12 years.

The researchers found that individuals in the uppermost quartile for either mid-life measures of central obesity (as measured by waist-to-hip ratio) or hypertension (blood pressure >140/90 or use of anti-hypertensive medication) displayed significantly poorer performance on executive function and visuomotor skills.

Loef and Walach

The reviewers performed a meta-analysis to assess the association between mid-life overweight (BMI 25 – 30kg/m2) or obesity (BMI > 30 kg/m2) and the risk of developing dementia later in life.

The reviewers found that being overweight or obese in mid-life led to a 1.34 and 1.91 times greater risk of developing dementia later in life, respectively.

Gorospe and Dave

The reviewers performed a systematic review of the available longitudinal cohort studies investigating the association between increased body mass index (BMI) and the risk of developing dementia. The researchers identified 8 cohort studies investigating the association between BMI and dementia, including 28,697 participants with 1,688 cases of dementia in study populations from Finland, France, Sweden, Japan, and the United States.

The reviewers reported that increased BMI is likely to be an independent risk factor for dementia. Specifically, the reviewers observed that those studies with appropriate exclusion of patients with dementia at baseline, enough power, and appropriate adjustment of potential confounders support this conclusion. Furthermore, the reviewers observed that studies with younger participants at baseline and longer follow-up periods showed the greatest associations.

Anstey et al.

The reviewers performed a systematic review and meta-analysis to assess the association between body mass index (BMI) in both mid-life and late-life and the risk of developing dementia. The reviewers identified 15 prospective studies in which the follow-up periods ranged from 3.2 – 36 years.

The reviewers found that a low BMI in mid-life was associated with a 1.96 times greater risk of developing Alzheimer’s disease while overweight and obese BMIs in mid-life were associated with 1.35 and 2.04 times greater risk respectively. The reviewers concluded that underweight, overweight and obesity in mid-life all increase the risk of developing dementia.

Beydoun et al.

The reviewers performed a systematic review and meta-analysis of prospective cohort studies to assess the association between obesity and overweight and the risk of developing dementia. The reviewers found 10 relevant prospective cohort studies in elderly adults (40 – 80 years at baseline) recording various adiposity measures, including body mass index (BMI) and waist circumference.

The reviewers observed that there was a significant U-shaped association between BMI and dementia, with the risk of developing dementia being increased for both obese and underweight individuals. Obese individuals had a 1.42 times greater risk of developing dementia than normal weight individuals and underweight individuals had a 1.36 times greater risk of developing dementia than normal weight individuals.

Based on these studies and reviews, it appears that having a high body mass index and waist circumference or waist-to-hip ratio in mid-life increase the risk of developing dementia in later life.

What are the other risk factors for dementia?

Various researchers have assessed the risk factors for dementia. In the preceding two sections, it was noted that two of the main risk factors for dementia are a lack of physical activity and poor body composition, as demonstrated by a high body mass index and/or a high waist-to-hip ratio. The following table sets out other risk factors not included in the above sections:

Study

Method

Finding

Plassman et al.

The researchers drew a sample of 856 individuals aged >71 years from the Aging, Demographics, and Memory Study sample, which was a group of people taken from the nationally representative Health and Retirement Study (HRS). The researchers evaluated these individuals for dementia using a comprehensive in-home assessment.

The researchers reported that in a representative sample of United States population, older age, fewer years of education, being African American and the presence of certain genetic traits (apolipoprotein (APOE) epsilon-4 alleles) were all associated with a higher risk of dementia.

Wang et al.

The researchers assessed whether greater levels of social interaction and intellectual stimulation are associated with a reduced risk of dementia in a longitudinal population-based study in Stockholm, Sweden.

The researchers reported that after adjusting for age, sex, education, cognitive functioning, comorbidity, depressive symptoms and physical functioning at the first examination, a more frequent participation in mental, social or otherwise productive activities was associated with a reduced risk of developing dementia.

Fabrigoule et al.

The researchers performed a prospective cohort study in 2,040 individuals aged >65 years living at home in Gironde, France, to assess the association between engagement in social and leisure activities and risk of developing dementia.

The researchers reported that almost all social and leisure activities reported were significantly associated with a lower risk of developing dementia.

Forti et al.

The researchers performed a prospective population-based study to assess the association between metabolic syndrome and dementia in older adults before and after the age of 75 years. The sample comprised 749 community-based subjects aged >65 years with no cognitive impairment at baseline.

The researchers found that the risk of developing any type of dementia was not associated with metabolic syndrome in subjects aged <75 years while it was in fact associated with a reduced risk of developing dementia in subjects aged >75 years.

Leibson et al.

The researchers performed a population-based cohort study to estimate of the effects of type II diabetes on the risk of developing dementia. The cohort included individuals with type II diabetes living in Rochester, Minnesota.

The researchers found that individuals with type II diabetes displayed a 1.66 times greater risk of all types of dementia than those who did not have the disease.

Hughes et al.

The researchers assessed the association between fruit and vegetable consumption in mid-life and the risk of developing all types of dementia in 3,779 members of the Swedish Twin Registry. The subjects completed a diet questionnaire around 30 years before cognitive screening for dementia. The researchers reported that 355 of the twins were diagnosed with dementia and 81 twin pairs were discordant for dementia.

The researchers found that a medium or large proportion of fruits and vegetables in the diet, compared with no fruits and vegetables or a small proportion of fruits and vegetables, was associated with a decreased risk of dementia. Therefore, the researchers suggested that a higher fruit and vegetable consumption may reduce the risk of dementia.

Anstey et al.

The reviewers performed a systematic review and meta-analysis to assess the association between smoking and the risk of developing dementia and cognitive decline. The review comprised 19 prospective studies with >12 months of follow-up.

The reviewers reported that individuals who were current smokers at baseline had a 1.79 times greater risk of Alzheimer's disease and a 1.27 times greater risk of any dementia than those who had never smoked. The reviewers also reported that individuals who were current smokers at baseline displayed greater yearly declines in Mini-Mental State Examination scores over the follow-up period than those who had never smoked.

Anstey et al.

The reviewers performed a systematic review and meta-analysis to assess the association between alcohol consumption and dementia and cognitive decline. The review comprised 15 prospective studies with follow-ups ranging from 2 – 8 years.

The reviewers found that never-drinkers had a 1.35 times greater risk of any type of dementia than light-to-moderate drinkers.

Anstey et al.

The reviewers performed a systematic review in order to assess the association between total serum cholesterol and dementia and cognitive decline. The reviewers obtained 18 prospective studies in which follow-ups ranged from 3 – 29 years and which included a total of 14,331 participants.

The reviewers found consistent associations between high midlife total cholesterol levels and an increased risk of all types of dementia. However, the reviewers did not find any evidence supporting an association between late-life total cholesterol levels and any type of dementia. The reviewers therefore suggest that the effect of total cholesterol levels on dementia risk occurs in mid-life but not in late-life.

Based on these studies, it appears that lifestyle features such as smoking, not eating enough fruits and vegetables, lower levels of social interaction and intellectual stimulation, and fewer years of education are risk factors for dementia, light-to-moderate alcohol consumption is not.

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Is general exercise useful for treating dementia?

A number of studies have investigated the use of either physical activity, general exercise or mixed-modality exercise training interventions for the treatment of dementia, as follows:

Study

Method

Finding

Stevens and Killeen

The researchers performed a randomized controlled trial to assess the effects of exercise on the progression of cognitive symptoms related to dementia and disability in 75 nursing home residents. The researchers randomly allocated the subjects to either an experimental or 1 of 2 control groups for a 12-week intervention. One of the control groups received no intervention and the other control group received a social interaction of the same duration and frequency as the exercise program. The exercise group performed a program of exercises 3 times per week for 30 minutes.

The researchers reported that the exercise group displayed a reduced rate of cognitive decline and an improvement in disability scores in comparison with the control groups.

Kwak et al.

The researchers performed a controlled trial to assess the effects of regular exercise on cognitive function and exercise capacity in 30 female senile dementia patients. The researchers divided the subjects into an exercise and a control group. The exercise group performed an exercise program 30 – 60 minutes per day, 2 – 3 times per week for 12 months while the control group did not. The researchers tested cognitive function, using the Mini-Mental State Examination (MSSE) score, Activities of Daily Living (ADL) and exercise capacity at baseline, at 6 months and after 12 months.

The researchers reported that the exercise group displayed significantly greater improvements in MSSE and ADL scores than the control group while exercise capacity also increased in the exercise group but not in the control group.

Eggermont et al.

The researchers performed a randomized controlled trial to assess the effects of a walking intervention on cognition in 97 older nursing home residents with an average age of 85.4 years with moderate dementia. The researchers randomly allocated the subjects to either an experimental or control condition. The experimental condition walked for 30 minutes, 5 days per week for 6 weeks while the control group received social visits with the same frequency. The researchers assessed performance in memory, executive function and total cognition before and after the exercise intervention.

The researchers did not find any differences between groups.

Kemoun et al.

The researchers performed a randomized controlled trial to assess the effects of a physical activity program comprised of walking, equilibrium and endurance exercises on cognitive function and walking efficiency in 31 subjects with an average age of 81.8 ± 5.3 years suffering from dementia. The researchers randomly allocated the subjects to either an experimental or control condition. The experimental group performed a 15-week physical activity program 3 times per week for 1-hour per session while the control group did not.

The researchers reported that the experimental group improved walking speed, stride length and score in the Rapid Evaluation of Cognitive Functions test while the control group decreased their equivalent measures.

Scherder et al.

The researchers performed a randomized controlled trial to examine whether physical activity leads to an improvement in cognitive function in 43 frail and elderly subjects with an average age of 86 years with mild cognitive impairment. The researchers randomly divided the subjects into 3 groups, including a walking group, a group performing hand and face exercises and a control group who all performed activities for 30 minutes a day, 3 times a week for 6 weeks. Before and after the intervention, the researchers measured cognitive functioning.

The researchers observed a strong but non-significant trend towards improved function in all cognitive in tasks in both of the exercise groups in comparison with the control group.

Edwards et al.

The researchers performed a pilot study to assess the effects of moderate-intensity, chair-based exercise on negative affect in 36 patients with a mean age of 86 years in 2 nursing homes. The subjects performed a 12-week exercise intervention involving sessions 3 times per week for 30-minutes at a moderate intensity. Before and after the intervention, the researchers measured affect using the Philadelphia Geriatric Center Apparent Affect Rating Scale.

The researchers reported that both anxiety and depression were significantly reduced after 12 weeks.

Heyn et al.

The reviewers performed a meta-analysis to assess the effectiveness of physical exercises in the treatment of dementia and related cognitive impairments. The reviewers limited the studies included within the meta-analysis to those which were randomized trials that assessed the role of exercise in subjects aged >65 years and who had a cognitive impairment.

The reviewers performed a meta-analysis to assess the effects of exercise programs on endurance and strength in both cognitively impaired (as defined by a Mini-Mental State Examination (MMSE) score of <23) and cognitively intact (as defined by a MMSE score of >24) older adults who participate in similar exercise programs. The reviewers found 41 studies that met the inclusion criteria, including 21 exercise trials with cognitively impaired individuals and 20 exercise trials with cognitively intact individuals.

The reviewers found no statistically significant difference in effect sizes in relation to either strength or endurance between the cognitively impaired individuals and the cognitively intact individuals. The reviewers therefore concluded that cognitively impaired older adults who take part in exercise programs will experience similar benefits in strength and endurance as healthy individuals of the same age.

Forbes et al.

The reviewers performed a Cochrane review to assess whether physical activity is able to delay the onset of dementia in healthy older adults and slow down the rate of cognitive decline. The reviewers sought randomized controlled trials in which physical activity programs were compared with usual care and which assessed the effects of physical activity on cognition, function, behaviour, depression and mortality in subjects with any type or degree of dementia. The reviewers identified 4 trials that met their inclusion criteria but since they were not provided with the data they requested from 2 of these, they only included 2 trials in their review.

The reviewers were unable to provide a conclusion regarding whether there is evidence that physical activity can improve or reduce the rate of decline in cognition, function, behaviour, depression and mortality in individuals with dementia.

Van Uffelen et al.

The reviewers performed a systematic review of randomized controlled trials to assess the effects of physical exercise on cognition in older adults with and without cognitive decline. The reviewers found 23 studies were included, involving 15 performed in cognitively healthy subjects and 8 performed in subjects with cognitive decline.

The reviewers reported that in cognitively healthy subjects, exercise displayed significant beneficial effects on information processing, executive function and memory. The reviewers also reported that in subjects with cognitive decline, exercise also displayed significant beneficial effects on general cognition, executive functions and memory.

Based on these studies and reviews, it appears very likely that exercise or physical activity interventions do improve strength, endurance and measures of physical function in activities of daily living (ADLS) in individuals with dementia. There are also strong indications that exercise or physical activity interventions do also reduce the rate of cognitive decline and alleviate anxiety and depression measures.

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Is aerobic exercise useful for treating dementia?

A number of studies and reviews have investigated the use of aerobic exercise interventions for the treatment of dementia, as follows:

Study

Method

Finding

Colcombe et al.

The researchers assessed whether aerobic fitness training in 59 sedentary people aged 60 – 79 years is able to increase brain volume in those regions that are associated with age-related cognitive decline. The subjects were randomly allocated to either aerobic fitness training or stretching and toning groups for a 6-month randomized clinical trial. Before and after the 6-month intervention, the researchers made high spatial resolution estimates of gray and white matter volume based on magnetic resonance imaging (MRI) scans as well as estimates of maximal oxygen uptake (VO2).

The researchers reported significant increases in brain volume in both gray and white matter regions following aerobic fitness training but following stretching and toning activities.

Baker et al.

The researchers performed a randomized controlled trial to assess the effects of aerobic exercise on cognition and other biomarkers associated with Alzheimer’s disease in 33 adults (17 females and 16 males) with amnestic mild cognitive impairment aged 55 – 85 years (mean = 70 years). The subjects were randomly allocated to either a high-intensity aerobic exercise group or to a stretching control group. The aerobic group exercised under supervision at 75 – 85% of heart rate reserve (HRR) for 45 – 60 minutes, 4 days per week for 6 months while the control group carried out supervised stretching activities at the same duration and frequency.

The researchers found that in females aerobic exercise improved performance in multiple tests of executive function, increased glucose disposal during the metabolic clamp and reduced fasting plasma levels of insulin, cortisol and brain-derived neurotrophic factor. In males, the researchers found that aerobic exercise only increased plasma levels of IGF-I and had a favorable effect only on a single measure of executive function performance.

Etnier et al.

The reviewers performed a meta-analysis to assess the relationship between aerobic fitness and cognitive performance.

The reviewers found that there was no significant linear or curvilinear relationship between aerobic fitness and cognitive function in cross-sectional post-test studies. However, since previous reviews have found a positive association between participation in physical activity and cognitive performance, the reviewers suggest that other physiological and psychological variables may mediate the relationship between increased physical activity and improved cognitive performance.

Smith et al.

The reviewers performed a systematic literature review of randomized controlled trials to assess the effect of aerobic exercise training on neurocognitive performance. The reviewers found 29 studies that met the inclusion criteria.

The reviewers found that groups performing aerobic exercise displayed modest improvements in attention and processing speed, executive function and memory in comparison with control groups.

Colcombe and Kramer

The reviewers performed a meta-analysis to assess the influence of enhancements in aerobic fitness on improvements in cognition in elderly people, subdivided into young-old (55 – 65 years), middle-old (66 – 70 years) and old-old (>71 years).

The reviewers found that improvements in aerobic fitness unequivocally lead to improvements in cognition, regardless of the type of cognitive task, the training method, or the characteristics of the subjects. The reviewers therefore concluded that their analysis establishes the efficacy of aerobic exercise as a method of enhancing the cognitive function of elderly people.

Based on these studies and reviews, there are good indications that aerobic exercise is able to improve cognitive function, regardless of the type of cognitive task, the training method, or the characteristics of the subjects (i.e. state of dementia). Such improvements may occur in tandem with beneficial increases in brain volume.

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Is resistance training useful for treating dementia?

A number of studies and reviews have investigated the use of resistance exercise interventions for the improvement of physical and cognitive function in elderly people, as follows:

Study

Method

Finding

Baum et al.

The researchers performed a prospective, randomized controlled, semi-crossover pilot study to assess whether an exercise program comprising both resistance-training and stretching could improve cognitive and physical function in 20 frail long-term care facility residents. The exercise program was performed for 1 hour, 3 times per week and involved seated range of motion (ROM) exercises and resistance-training using elastic resistance bands and soft weights. The control group also met 3 times per week and participated in other non-physically demanding activities such as painting. Before and after the intervention, the researchers assessed physical function using the Timed Up-and-Go (TUG) test, Berg balance scale and physical performance test (PPT), and cognitive function using the Mini-Mental Status Examination (MMSE).

The researchers reported that the exercise group significantly improved in all 4 tests, demonstrating that resistance-training and stretching was able to improve both physical and cognitive function.

Perrig-Chiello et al.

The researchers assessed the short- and long-term effects of resistance-training on muscular strength, psychological well-being, control-beliefs, cognitive speed and memory in 46 active, elderly people with an average age of 73.2 years. The researchers randomly allocated the subjects to either an exercise group or a control group. The exercise group performed 8 resistance exercises once per week for 8 weeks.

The researchers reported that the exercise group significantly improved muscular strength and significantly decreased self-attentiveness, which is associated with improved psychological well-being. The researchers also observed a trend towards improved cognitive functioning, including recognition and free recall.

Liu-Ambrose et al.

The researchers performed a single-blinded randomised trial to assess the effects of resistance-training on cognitive function in 155 community-dwelling women aged 65 – 75 years living in Vancouver, Canada. The researchers randomly allocated the subjects either to 1 of 2 resistance-training groups, or to a balance and tone training control group. The resistance-training groups differed insofar as 1 performed training once per week and the other performed the training twice per week. The resistance-training was performed in classes of 60 minutes in duration, with a 10-minute warm-up, 40 minutes of training content and a 10-minute cool-down. The exercises comprised both machine exercises and free weights including biceps curls, triceps extensions, seated rows, lat pull-downs, leg presses, hamstring curls and calf raises performed for 2 sets of 6 – 8 repetitions.

The researchers reported that both of the resistance training groups significantly improved their performance on the Stroop Test of cognitive function compared with those in the control group.

Tsutsumi et al.

The researchers assessed the psychological and behavioral adaptations in response to 12 weeks of resistance-training in medically healthy but sedentary 42 older adults with an average age of 68 years. The researchers randomly allocated the subjects to either a high intensity-low volume resistance-training group (2 sets of 8 – 10 repetitions for 75 – 85% of 1RM), a low intensity-high volume resistance-training group (2 sets of 14 – 16 repetitions for 55 – 65% of 1RM), or to a control group.

The researchers assessed the effects of 12 months of twice-weekly resistance-training on functional plasticity in in community-dwelling elderly females.

The researchers reported that the exercise intervention led to improvements in task performance that occurred in tandem with functional changes in 2 regions of cortex previously associated with response inhibition processes (the anterior portion of the left middle temporal gyrus and the left anterior insula extending into lateral orbital frontal cortex).

Özkaya et al.

The researchers assessed the effects of strength and endurance training on cognition, as evaluated by event-related potentials (ERP), in 36 elderly subjects, aged 60 – 85 years. The researchers randomly allocated the subjects into 3 groups: sedentary control, strength training, and endurance training. The training groups trained 3 times per week. Before and after the 9-week exercise intervention, the researchers measured functional fitness performance and ERPs.

The researchers reported that functional fitness performance improved significantly in both training groups. They also noted significant changes in ERP measurements in the training groups, which suggested that resistance-training may improve early sensory processing and cognitive functioning in elderly people.

Based on these studies and reviews, there are some indications that resistance exercise may be able to help improve cognitive function and alleviate anxiety and negative mood in elderly populations in addition to the known positive effects on physical function.

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What is the economic burden of dementia?

A small number of studies have either reviewed the economic burden of dementia or have assessed the economic validity of exercise treatments in relation to dementia, as follows:

Study

Finding

Wimo et al.

The researchers assessed the worldwide costs of dementia using a model that combined prevalence figures for each regions and cost-of-illness studies from countries for which there was good data, adjusted for each country based on a relationship between known direct costs of care per person and the gross domestic product per capita. The researchers estimated that the worldwide annual direct costs for dementia in 2003 were $156 billion, assuming a worldwide prevalence of 27.7 million people with dementia.

Based on this study, the worldwide annual direct costs for dementia in 2003 are likely to be around $156 billion, assuming a worldwide prevalence of 27.7 million people with dementia.

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Conclusions

On the basis of these studies and reviews, the following conclusions might be drawn:

Area

Conclusion

Low levels of physical activity is a risk factor

It appears very likely that individuals who habitually perform low levels of physical activity are at increased risk of developing dementia in later life.

Poor body composition is a risk factor

It appears very likely that having a high body mass index and waist circumference or waist-to-hip ratio in mid-life increase the risk of developing dementia in later life.

Exercise and physical activity interventions

It seems very likely that general or multi-modal exercise interventions or physical activity programs do improve strength, endurance and measures of physical function in activities of daily living (ADLS) in individuals with dementia. There are also strong indications that exercise or physical activity interventions do also reduce the rate of cognitive decline and alleviate anxiety and depression measures.

Aerobic exercise

There are good indications that aerobic exercise is able to improve cognitive function, regardless of the type of cognitive task, the training method, or the characteristics of the subjects (i.e. state of dementia). Such improvements may occur in tandem with beneficial increases in brain volume.

Resistance training

There are some indications that resistance exercise may be able to help improve cognitive function and alleviate anxiety and negative mood in elderly populations in addition to the known positive effects on physical function.

The research indicates that low levels of physical activity and poor body composition during mid-life are risk factors for developing dementia later in life. However, general physical activity, multi-modal exercise, aerobic exercise and resistance-training may all help improve various measures of physical and cognitive function in elderly people with dementia.

Jorm, A. F., Dear, K. B., & Burgess, N. M. (2005). Projections of future numbers of dementia cases in Australia with and without prevention. The Australian and New Zealand journal of psychiatry, 39(11-12), 959.

Anstey, K. J., Cherbuin, N., Budge, M., & Young, J. (2011). Body mass index in midlife and late-life as a risk factor for dementia: a meta-analysis of prospective studies. Obesity reviews: an official journal of the International Association for the Study of Obesity, 12(5), e426.

Beydoun, M. A., Beydoun, H. A., & Wang, Y. (2008). Obesity and central obesity as risk factors for incident dementia and its subtypes: a systematic review and meta-analysis. Obesity reviews: an official journal of the International Association for the Study of Obesity, 9(3), 204.

Anstey, K. J., Mack, H. A., & Cherbuin, N. (2009). Alcohol consumption as a risk factor for dementia and cognitive decline: meta-analysis of prospective studies. The American journal of geriatric psychiatry: official journal of the American Association for Geriatric Psychiatry, 17(7), 542.

Anstey, K. J., Lipnicki, D. M., & Low, L. F. (2008). Cholesterol as a risk factor for dementia and cognitive decline: a systematic review of prospective studies with meta-analysis. The American journal of geriatric psychiatry: official journal of the American Association for Geriatric Psychiatry, 16(5), 343.